U.S. patent application number 15/185735 was filed with the patent office on 2016-10-06 for high voltage resistor with high voltage junction termination.
The applicant listed for this patent is Taiwan Semiconductor Manufacturing Company, Ltd.. Invention is credited to Chih-Chang CHENG, Ruey-Hsin LIU, Ru-Yi SU, Chun Lin TSAI, Fu-Chih YANG.
Application Number | 20160293694 15/185735 |
Document ID | / |
Family ID | 47614308 |
Filed Date | 2016-10-06 |
United States Patent
Application |
20160293694 |
Kind Code |
A1 |
SU; Ru-Yi ; et al. |
October 6, 2016 |
HIGH VOLTAGE RESISTOR WITH HIGH VOLTAGE JUNCTION TERMINATION
Abstract
High voltage semiconductor devices are described herein. An
exemplary semiconductor device includes a first doped region and a
second doped region disposed in a substrate. The first doped region
and the second doped region are oppositely doped and adjacently
disposed in the substrate. A first isolation structure and a second
isolation structure are disposed over the substrate, such that each
are disposed at least partially over the first doped region. The
first isolation structure is spaced apart from the second isolation
structure. A resistor is disposed over a portion of the first
isolation structure and electrically coupled to the first doped
region. A field plate disposed over a portion of the second doped
region and electrically coupled to the second doped region.
Inventors: |
SU; Ru-Yi; (Yunlin County,
TW) ; YANG; Fu-Chih; (Fengshan City, TW) ;
TSAI; Chun Lin; (Hsin-Chu, TW) ; CHENG;
Chih-Chang; (Hsin-Chu, TW) ; LIU; Ruey-Hsin;
(Hsin-Chu, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Taiwan Semiconductor Manufacturing Company, Ltd. |
Hsin-Chu |
|
TW |
|
|
Family ID: |
47614308 |
Appl. No.: |
15/185735 |
Filed: |
June 17, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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13195156 |
Aug 1, 2011 |
9373619 |
|
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15185735 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 29/36 20130101;
H01L 29/66136 20130101; H01L 28/20 20130101; H01L 29/0623 20130101;
H01L 29/404 20130101; H01L 29/063 20130101; H01L 29/405 20130101;
H01L 29/7835 20130101; H01L 23/535 20130101; H01L 27/0802 20130101;
H01L 29/0646 20130101; H01L 29/8611 20130101 |
International
Class: |
H01L 29/06 20060101
H01L029/06; H01L 29/40 20060101 H01L029/40; H01L 29/66 20060101
H01L029/66; H01L 49/02 20060101 H01L049/02; H01L 29/861 20060101
H01L029/861; H01L 29/36 20060101 H01L029/36; H01L 23/535 20060101
H01L023/535 |
Claims
1. A semiconductor device comprising: a first doped region and a
second doped region disposed in a substrate, the first doped region
and the second doped region being oppositely doped and being
adjacently disposed in the substrate; a first isolation structure
and a second isolation structure each disposed over the substrate,
the first isolation structure and the second isolation structures
being spaced apart from one another and each being disposed at
least partially over the first doped region; a resistor disposed
over a portion of the first isolation structure and electrically
coupled to the first doped region; and a field plate disposed over
a portion of the second doped region and electrically coupled to
the second doped region.
2. The semiconductor device of claim 1, wherein a non-distal
portion of the resistor is electrically coupled to the first doped
region.
3. The semiconductor device of claim 2, wherein the resistor has a
length L, and the non-distal portion of the resistor is located
away from a distal end of the resistor by a distance that is in a
range from about 0.4*L to about 0.6*L.
4. The semiconductor device of claim 2, further comprising an
interconnect structure, wherein the interconnect structure
includes: a first contact electrically coupled to the first doped
region; a second contact electrically coupled to the non-distal
portion of the resistor; and an interconnect line electrically
coupled to the first contact and the second contact.
5. The semiconductor device of claim 4, wherein: the resistor
includes a first distal end opposite a second distal end; and the
interconnect structure further includes a first terminal
electrically coupled to the first distal end and a second terminal
electrically coupled to the second distal end.
7. The semiconductor device of claim 1, further comprising: a third
doped region disposed in the first doped region, wherein the third
doped region has a same doping polarity as the first doped region
and a higher doping concentration than the first doped region, and
further wherein the resistor is electrically coupled to the third
doped region; and a fourth doped region disposed in the second
doped region, wherein the fourth doped region has a same doping
polarity as the second doped region and a higher doping
concentration than the second doped region, and further wherein the
field plate is electrically coupled to the fourth doped region.
8. The semiconductor device of claim 7, wherein a P/N junction is
between the first doped region and the second doped region, the
semiconductor device further comprising: a fifth doped region
disposed in the first doped region, the fifth doped region having
an opposite doping polarity than the first doped region, wherein
the fifth doped region is disposed in the first doped region to
provide at least one additional P/N junction.
9. A semiconductor device, comprising: a diode-based high-voltage
junction termination (HVJT) device, the diode-based HVJT device
having: a first doped region and a second doped region disposed in
a substrate, the first doped region and the second doped region
having opposite doping polarities and being adjacently disposed in
the substrate, a cathode terminal electrically coupled to the first
doped region, and an anode terminal electrically coupled to the
second doped region; an isolation structure disposed over a portion
of the first doped region; and a resistor disposed over a portion
of the isolation structure, wherein the resistor is electrically
coupled to the diode-based HVJT device.
10. The semiconductor device of claim 9, wherein the diode-based
HVJT device further includes a third doped region disposed in the
first doped region, the third doped region having an opposite
doping polarity than the first doped region.
11. The semiconductor device of claim 10, wherein the HVJT device
includes a first P/N junction between the first doped region and
the second doped region and a second P/N junction between the third
doped region and the first doped region.
12. The semiconductor device of claim 10, wherein the HVJT device
includes a first P/N junction between the first doped region and
the second doped region, a second P/N junction between a top
surface of the third doped region and the first doped region, and a
third P/N junction between a bottom surface of the third doped
region and the first doped region.
13. The semiconductor device of claim 9, wherein the diode-based
HVJT device further includes: a first heavily doped region disposed
in the first doped region, wherein the first heavily doped region
has a same doping polarity as the first doped region and a higher
doping concentration than the first doped region, and further
wherein the cathode terminal is electrically coupled to the first
heavily doped region; a second heavily doped region disposed in the
second doped region, wherein the second heavily doped region has a
same doping polarity as the second doped region and a higher doping
concentration than the second doped region, and further wherein the
anode terminal is electrically coupled to the second heavily doped
region.
14. The semiconductor device of claim 13, wherein: the cathode
terminal includes a contact disposed on the first heavily doped
region; and the anode terminal includes a field plate disposed on
the second heavily doped region.
15. The semiconductor device of claim 9, wherein the first doped
region is electrically coupled to an approximate midpoint of the
resistor.
16. A method for fabricating a semiconductor device, the method
comprising: forming a first doped region in a substrate; forming a
second doped region adjacent to the first doped region in the
substrate, such that a P/N junction is formed between the first
doped region and the second doped region, the first doped region
and the second doped region being oppositely doped; forming an
isolation structure over a portion of the first doped region;
forming a field plate over and electrically coupled to the second
doped region; and forming a resistor over the isolation structure
and electrically coupled to the first doped region.
17. The method of claim 16, wherein the forming the resistor is
carried out in a manner such that the resistor includes a
non-distal portion located between a first distal end opposite a
second distal end, the non-distal portion being electrically
coupled to the first doped region.
18. The method of claim 16, further comprising forming an
interconnect structure that electrically couples the resistor to
the first doped region, the interconnect structure including: a
first contact electrically coupled to the first doped region; a
second contact electrically coupled to the non-distal portion of
the resistor; and an interconnect line electrically coupled to the
first contact and the second contact.
19. The method of claim 16, further comprising: forming a third
doped region in the first doped region, wherein the third doped
region has a same doping polarity as the first doped region and a
higher doping concentration than the first doped region, the
resistor being electrically coupled to the third doped region; and
forming a fourth doped region in the second doped region, wherein
the fourth doped region has a same doping polarity as the second
doped region and a higher doping concentration than the second
doped region, the field plate being electrically coupled to the
fourth doped region.
20. The method of claim 19, further comprising: forming a fifth
doped region disposed in the first doped region, the fifth doped
region having an opposite doping polarity than the first doped
region, such that at least one additional P/N junction is formed
between the fifth doped region and the first doped region.
Description
PRIORITY DATA
[0001] The present application is a continuation application of
U.S. patent application Ser. No. 13/195,156, filed Aug. 1, 2011,
which is hereby incorporated by reference in its entirety
BACKGROUND
[0002] The semiconductor integrated circuit (IC) industry has
experienced rapid growth. Technological advances in IC materials
and design have produced generations of ICs where each generation
has smaller and more complex circuits than the previous generation.
However, these advances have increased the complexity of processing
and manufacturing ICs and, for these advances to be realized,
similar developments in IC processing and manufacturing are needed.
In the course of IC evolution, functional density (i.e., the number
of interconnected devices per chip area) has generally increased
while geometry size (i.e., the smallest component that can be
created using a fabrication process) has decreased.
[0003] Various types of passive circuit components may be
fabricated on a semiconductor wafer. For example, a resistor may be
formed as a passive circuit component on a wafer. Some applications
require these resistors to withstand high voltages, for example
voltages as high as a few hundred volts. However, conventional high
voltage resistors may suffer from device breakdown issues before a
sufficiently-high voltage is reached. For example, conventional
high voltage resistors may rely on using a P/N junction to sustain
a breakdown voltage. Junction breakdown is limited by doping
concentration, which has not been optimized in conventional high
voltage resistors.
[0004] Therefore, while existing high voltage resistor devices have
been generally adequate for their intended purposes, they have not
been entirely satisfactory in every aspect.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] Aspects of the present disclosure are best understood from
the following detailed description when read with the accompanying
figures. It is emphasized that, in accordance with the standard
practice in the industry, various features are not drawn to scale.
In fact, the dimensions of the various features may be arbitrarily
increased or reduced for clarity of discussion.
[0006] FIG. 1 is a flowchart illustrating a method for fabricating
a high voltage semiconductor device according to various aspects of
the present disclosure.
[0007] FIGS. 2-13 are diagrammatic fragmentary cross-sectional side
views of a portion of a wafer at various stages of fabrication in
accordance with various aspects of the present disclosure.
[0008] FIGS. 14-17 are simplified top views of different
embodiments of a high voltage resistor according to various aspects
of the present disclosure, respectively.
[0009] FIG. 18 is a chart illustrating a relationship between
breakdown voltage VS electrical biasing voltage of a high voltage
N-well according to various aspects of the present disclosure.
[0010] FIG. 19 is a chart graphically illustrating a voltage
breakdown.
DETAILED DESCRIPTION
[0011] It is to be understood that the following disclosure
provides many different embodiments, or examples, for implementing
different features of the invention. Specific examples of
components and arrangements are described below to simplify the
present disclosure. These are, of course, merely examples and are
not intended to be limiting. Moreover, the formation of a first
feature over or on a second feature in the description that follows
may include embodiments in which the first and second features are
formed in direct contact, and may also include embodiments in which
additional features may be formed interposing the first and second
features, such that the first and second features may not be in
direct contact. Various features may be arbitrarily drawn in
different scales for the sake of simplicity and clarity.
[0012] Illustrated in FIG. 1 is a flowchart of a method 10
according to various aspects of the present disclosure. The method
10 includes block 12 in which a first doped region is formed in a
substrate. The method 10 includes block 14 in which a second doped
region is formed in the substrate. The second doped region is
oppositely doped from the first doped region. An interface between
the first and second doped regions forms a P/N junction. The method
10 includes block 16 in which first and second isolation structures
are formed over the first doped region. The method 10 includes
block 18 in which a resistor device is formed over the first
isolation structure. The method 10 includes block 20 in which a
field plate is formed at least partially over the second isolation
structure. The field plate is disposed over the P/N junction.
[0013] FIGS. 2-13 are diagrammatic fragmentary cross-sectional side
views of various portions of a semiconductor wafer at various
fabrication stages according to embodiments of the present
disclosure. It is understood that FIGS. 2 to 13 have been
simplified for a better understanding of the inventive concepts of
the present disclosure.
[0014] Referring to FIG. 2, a portion of a substrate 30 is
illustrated. The substrate 30 is doped with a P-type dopant such as
boron. In another embodiment, the substrate 30 may be doped with an
N-type dopant such as phosphorous or arsenic. The substrate 30 may
also include other suitable elementary semiconductor materials,
such as diamond or germanium; a suitable compound semiconductor,
such as silicon carbide, indium arsenide, or indium phosphide; or a
suitable alloy semiconductor, such as silicon germanium carbide,
gallium arsenic phosphide, or gallium indium phosphide.
[0015] A buried well 35 is formed in a portion of the substrate 30
through an ion implantation process known in the art. The buried
well 35 is formed to have an opposite doping polarity to that of
the substrate 30. In the illustrated embodiment, the buried well 35
is N-type doped, since the substrate 30 herein is a P-type
substrate. In another embodiment where the substrate 30 is an
N-type substrate, the buried well 35 is P-type doped. The buried
well 35 may be formed by an implantation process having a dose that
is in a range from about 1.times.10.sup.12 atoms/centimeter.sup.2
to about 2.times.10.sup.12 atoms/centimeter.sup.2. The buried well
35 may have a doping concentration that is in a range from about
1.times.10.sup.15 atoms/centimeter.sup.3 to about 1.times.10.sup.16
atoms/centimeter.sup.3. It is understood that a patterned
photoresist layer may be formed over an upper surface of the
substrate before the implantation process is performed. The
patterned photoresist layer serves as a mask during the
implantation process. After the formation of the buried well 35, an
epitaxial growth process 40 is performed to form an epi-layer 45
over the substrate 30 and over the buried well 35.
[0016] Referring now to FIG. 3, a high-voltage doped well 50 is
formed in the substrate 30. The high-voltage doped well 50 is
formed by an ion implantation process known in the art. For
example, the doped well 50 may be formed by an implantation process
having a dose that is in a range from about 3.times.10.sup.12
atoms/centimeter.sup.2 to about 4.times.10.sup.12
atoms/centimeter.sup.2. In an embodiment, the high-voltage doped
well has a doping concentration that is in a range from about
1.times.10.sup.15 atoms/centimeter.sup.3 to about 1.times.10.sup.16
atoms/centimeter.sup.3. A patterned photoresist layer (not
illustrated) may be formed over the substrate 35 as a mask during
the implantation process. The high-voltage doped well 50 is doped
with the same doping polarity as the buried well 35 (opposite from
that of the substrate 30). Thus, the high-voltage doped well is a
high-voltage N-well (HVNW) in the illustrated embodiment. The
high-voltage 50 is formed in a manner such that it surrounds the
buried well 35. It is understood that in some embodiments, the
buried well 35 may be considered to be a part of the high-voltage
50, or that they may be collectively referred to as an N-drift
region or as HVNW/BNW. For the sake of simplicity, the buried well
35 is not specifically shown in the following Figures.
[0017] Referring now to FIG. 4, doped wells 60 are formed in
portions of the substrate adjacent to the N-drift region 50. In an
embodiment, the doped wells 60 cover the epi-layer 45. The doped
wells 60 may be formed by an ion implantation process known in the
art. The doped wells 60 are doped with the same doping polarity as
that of the substrate 30 (and opposite of the N-drift region 50).
Thus, in the embodiment shown, the doped wells 60 are formed to be
P-wells. In an embodiment, the doped wells 60 are formed using an
ion implantation process and has a concentration level that is in a
range from about 5.times.10.sup.15 atoms/centimeter.sup.3 to about
5.times.10.sup.16 atoms/centimeter.sup.3.
[0018] Still referring to FIG. 4, a doped well 70 is formed in the
N-drift region 50. The doped well 70 is formed using another ion
implantation process known in the art. The doped well has the same
doping polarity as the N-drift region 50 and has a greater doping
concentration level than the N-drift region 50. Thus, in the
embodiment shown, the doped well 70 is a more heavily-doped N-well.
In an embodiment, the doped well 70 has a doping concentration
level that is in a range from about 1.times.10.sup.16
atoms/centimeter.sup.3 to about 1.times.10.sup.17
atoms/centimeter.sup.3.
[0019] Referring now to FIG. 5, isolation structures 80-81 are
formed over the N-drift region 50, and an isolation structure 82 is
formed over the doped well 70. The isolation structures 80-82 may
include a dielectric material. The isolation structure 82 has a
thickness 90. In an embodiment, the thickness 90 is in a range from
about 0.2 microns (um) to about 1 um. In the embodiment shown in
FIG. 5, the isolation structures 80-82 are Local Oxidation of
Silicon (LOCOS) devices (also referred to as field oxide). The
LOCOS devices may be formed using a nitride mask and
thermal-growing an oxide material through the mask openings.
Alternatively, the isolation structures 80-82 may include shallow
trench isolation (STI) devices or deep trench isolation (DTI)
devices. Thereafter, active regions of transistors are defined,
which may include source/drain regions of a Field Effect Transistor
(FET) device.
[0020] Referring now to FIG. 6, a resistor device 100 is formed
over the isolation structure 82. The resistor device 100 has an
elongate and winding shape. In one embodiment, the resistor device
100 has a zig-zag (or an S shape). In another embodiment, the
resistor device 100 has a spiral shape. In yet another embodiment,
the resistor device 100 has a square shape. These shapes will be
more clearly viewed with reference to FIGS. 14-17 below, which
illustrate top views of various embodiments of the resistor device
100. In the cross-sectional view shown in FIG. 6, the resistor
device 100 appears as a plurality of resistor blocks 100A-100G. It
is understood, however, that these resistor blocks 100A-100G are
actually parts of an individual elongate resistor device.
[0021] In an embodiment, the resistor device 100 includes a
polysilicon material, and may therefore be referred to as a
polysilicon resistor. The polysilicon resistor 100 is designed to
handle high voltages, for example voltages greater than about 100
volts, and may be as high as a few hundred volts. Thus, the
polysilicon resistor 100 may also be referred to as a high voltage
device. In that case, the polysilicon resistor 100 may be formed at
the same time as when other high voltage polysilicon gates are
formed. In other words, the polysilicon resistor 100 may be formed
using the same processes that form other high voltage polysilicon
gates.
[0022] Thereafter, heavily doped regions 110-111 are formed at the
upper surface of the doped well 70 and adjacent the isolation
structure 82. In the embodiment shown, the heavily doped regions
110-111 are formed in between the isolation structures 80-82 and
81-82, respectively. The heavily doped regions 110-111 may be
formed by one or more ion implantation processes. The heavily doped
regions 110-111 have the same doping polarity (in this case N-type)
as the doped well 70, but with a higher doping concentration. The
heavily doped regions 110-111 have a doping concentration level
that is in a range from about 1.times.10.sup.19
atoms/centimeter.sup.3 to about 1.times.10.sup.20
atoms/centimeter.sup.3.
[0023] Heavily doped regions 112-113 are also formed at the upper
surface of the doped wells 60. In one embodiment, the heavily doped
regions 112-113 have the same doping polarity as the doped wells 60
(P-type herein). In another embodiment, the heavily doped regions
112-113 may contain a heavily doped N-type portion as well as a
heavily doped P-type portion.
[0024] A plurality of field plates 120-123 are also formed. In an
embodiment, the field plate 120 is formed over an interface between
the doped well 60 and the N-drift region 50. In other words, the
field plate 120 is formed partially over the doped well 60 and
partially over the isolation structure 80. In a similar manner, the
field plate 121 is formed over an interface between the doped well
60 and the N-drift region 50 and formed partially over the
isolation structure 81. The field plates 122-123 are formed over
the heavily doped regions 112-113, respectively. It is also
understood that field plates may be formed over the heavily doped
regions 110-111, but they are not shown herein for the sake of
simplicity.
[0025] In an embodiment, the field plates 120-123 contain a
polysilicon material. In another embodiment, the field plates
120-123 contain a metal material. One or more of the field plates
120-123 may be formed using the same process that forms the
resistor device 100 (formed at the same time as the resistor device
100). It is understood that the field plates 120-121 may serve as
gate terminals of a transistor device, and the field plates 122-123
may serve as source terminals of the transistor device. The field
plates 120-123 are coupled to electrical ground. Thus, the
corresponding transistors each have their source and gate terminals
grounded and would therefore operate in a reverse mode (i.e., the
transistors are turned off). The field plates 120-123 held release
or relieve the electric field in the substrate 30 (and in the
various doped regions/wells formed within).
[0026] The field plates 120-123, the doped wells 50 and 60, and the
isolation structures 80-81 collectively form high-voltage junction
termination (HVJT) devices 130-131. The HVJT devices 130-131 help
improve a breakdown voltage of the resistor device 100 through the
field plates 120-123 as well as P/N junctions formed by the doped
wells 50 and 60. The field plates 120-123 and the P/N junctions
reduce the intensity of the electric field near the resistor device
100. As a result, the resistor device 100 can tolerate a greater
voltage (compared to conventional resistor devices) before
experiencing device breakdown.
[0027] Referring now to FIG. 7, an interconnect structure 150 is
formed over the isolation structures 80-82, the heavily doped
regions 110-113, and the resistor device 100. The interconnect
structure 150 includes a plurality of patterned dielectric layers
and conductive layers that provide interconnections (e.g., wiring)
between circuitries, inputs/outputs, and various doped features
(for example, the N-drift region 50). In more detail, the
interconnect structure 150 may include a plurality of interconnect
layers, also referred to as metal layers. Each of the interconnect
layers includes a plurality of interconnect features, also referred
to as metal lines. The metal lines may be aluminum interconnect
lines or copper interconnect lines, and may include conductive
materials such as aluminum, copper, aluminum alloy, copper alloy,
aluminum/silicon/copper alloy, titanium, titanium nitride,
tantalum, tantalum nitride, tungsten, polysilicon, metal silicide,
or combinations thereof. The metal lines may be formed by a process
including physical vapor deposition (PVD), chemical vapor
deposition (CVD), sputtering, plating, or combinations thereof.
[0028] The interconnect structure 150 includes an interlayer
dielectric (ILD) that provides isolation between the interconnect
layers. The ILD may include a dielectric material such as a low-k
material or an oxide material. The interconnect structure 150 also
includes a plurality of contacts/contacts that provide electrical
connections between the different interconnect layers and/or the
features on the substrate, such as the doped well 70 or the
resistor device 100.
[0029] As part of the interconnect structure, a contact 160 is
formed on the heavily doped region 110. As such, the contact 160 is
electrically coupled to the heavily doped region 110 and therefore
electrically coupled to the doped well 70. An electrical bias can
be applied to the doped well 70 through the contact 160. Meanwhile,
another contact 161 is formed on a segment 100D of the resistor
device. The segment 100D is located between two opposite distal
ends of the resistor device 100 (e.g., 100A and 100G), and it is
located at or near a midpoint of the resistor device 100.
[0030] The midpoint of the resistor device is a point on the
resistor device that is equidistant from the two opposite distal
ends. As an example, if the resistor device 100 has a total length
L that is measured along all the windings or turns of the resistor
device, then the midpoint of the resistor device 100 is a point
that is 0.5*L away from either of the two distal ends. Resistance
of a device is a function of the device's length, width, height,
and material. Thus, in an embodiment where the resistor device 100
has a relatively uniform width, height, and material composition
throughout, the resistance of the portion of the resistor device on
either side of the midpoint is 0.5*(overall resistance of the
resistor device). According to Kirchhoff's law,
voltage=current*resistance. Thus, as current remains fixed, voltage
varies linearly with resistance. This means that a voltage at the
midpoint of the resistor device is about
0.5*(V.sub.High-V.sub.Low), wherein V.sub.High is defined as the
high voltage at one of the distal ends, and V.sub.low is defined as
the low voltage at one of the distal ends (which is typically
electrically grounded).
[0031] In the present embodiment, the segment 100D (coupled to the
contact 161) is within 0.1*L of the midpoint of the resistor device
100, where L=overall length of the resistor device. Stated
differently, the segment may be at, or no farther than, 0.1*L away
from the midpoint. Another way of expressing this relationship is
that a distance between the segment 100D and either the distal end
100A or the distal end 100G is in a range from about 0.4*L to about
0.6*L.
[0032] The interconnect structure 150 includes a metal line (or
interconnect line) 170 that is electrically coupled to both the
contact 160 and the contact 161. In this manner, the doped well 70
is electrically biased to the same voltage as the segment 100D of
the resistor device. In other words, the voltage at the segmented
100D--which will be a percentage of the voltage applied to one of
the distal ends of the resistor device 100--will be the voltage at
the doped well 70. This type of biasing scheme offers advantages,
which will be discussed below in more detail.
[0033] Referring now to FIG. 8, the distal end 100A of the resistor
device is coupled to a terminal 200, and the distal end 100G of the
resistor device is coupled to a terminal 201. The terminals 200 and
201 include conductive materials such as Al or Cu, or combinations
thereof. The terminals 200 and 201 may be electrically coupled to
the distal ends 100A and 100G through one or more respective
contacts/contacts and/or metal lines, which are not necessarily
illustrated in detail herein for the sake of simplicity. The
terminals 200-201 also may or may not be formed directly over the
resistor device 100.
[0034] The terminals 200 and 201 serve as electrical input/output
points (or access points) for the resistor device 100. For example,
a high voltage (on the order of a few hundred volts) can be applied
to the terminal 200 while the terminal 201 can be grounded. Vice
versa, a high voltage can be applied to the terminal 201 while the
terminal 200 can be grounded.
[0035] As discussed above, the segment 100D experiences only a
fraction of the high voltage applied at either the terminal 200 or
the terminal 201. As an example, in an embodiment where a voltage
of about 500 volts is applied to the terminal 201 and the terminal
200 is grounded, and where the segment 100D is located
substantially at the midpoint of the resistor device 100, then the
voltage at the segment 100D will be about 250 volts. As the
location of segment 100D moves away from the midpoint and toward
either the distal ends 100A or 100G, the voltage measured at the
segment 100D will also drift away from 250 volts.
[0036] In an embodiment where V.sub.High is applied at one of the
terminals 200-201, and the other one of the terminals is grounded,
and the location of segment 100D is within 0.1*L away from the
midpoint of the resistor device, then the voltage at the segment
100D will be in a range from about 0.4*V.sub.High to about
0.6*V.sub.High, for example at about 0.5*V.sub.High. Since the
heavily doped region 110 (and therefore the doped well 70) is tied
to segment 100D, this means the doped well 70 is electrically
biased to the voltage at segment 100D. In other words, the doped
well 70 is electrically biased close to a middle of the voltage
difference between the two terminals 200-201, which is not done in
conventional high voltage devices. Thus, for conventional high
voltage devices, a high voltage potential exists between the doped
well 70 and one of the distal ends of the resistor device. The
device may suffer breakdown issues caused by such high voltage
potential. The device breakdown is typically limited by the
thickness 90 of the isolation structure 82. Typically, the
conventional high voltage devices may experience device breakdown
issues when V.sub.High exceeds about 470 volts.
[0037] In comparison, the embodiments herein electrically biases
the doped well 70 to have a voltage that is close to a middle of
the voltage difference between the two terminals 200-201. As such,
the device can tolerate a higher voltage difference before
breakdown occurs, since the voltage at the doped well 70 is not too
different from either V.sub.High or V.sub.Low. As an example, the
device herein can tolerate a voltage difference of about 730 volts
in an embodiment, as the doped well 70 is biased to about half of
730 volts, which is about 365 volts. Stated differently, the device
only needs to tolerate about 365 volts to enable a high voltage of
about 730 volts to be applied to one of its terminals (the other
terminal is grounded). Meanwhile, the thickness 90 of the isolation
structure can remain about the same as conventional devices, since
the embodiments herein need not rely on increase in thickness of
the isolation structure 82 to improve its tolerance of high
voltages. Additionally, the biased doped well 70 may also extend a
depletion region in the substrate 30, which may further improve the
device's electrical performance.
[0038] The HVJT devices 130-131 also help increase the breakdown
voltage of the resistor device 100. In conventional high-voltage
structures without the HVJT devices 130-131, a high electric field
is concentrated near a P/N junction formed at a P-well and a
high-voltage N-well. This concentrated electric field may have a
sharp shape (e.g., a triangular shape) and may cause device
breakdown at voltages less than about 100 volts. In comparison, by
forming the HVJT device 130-131, the high-voltage device of the
present disclosure may change the shape of the electric field to a
more trapezoidal shape. Breakdown voltage is an integral over the
area of the electric field. Due at least in part to its larger
area, the trapezoidal-shaped electric field herein will yield a
larger integral than traditional triangular-shaped electric fields.
As such, the breakdown voltage is increased. Furthermore, the field
plates 120-123 of the HVJT devices 130-131 also help reduce the
intensity of the electric field, thereby further alleviating the
breakdown issues.
[0039] FIGS. 2-8 illustrate one embodiment of the high-voltage
semiconductor device, which implements the HVJT according to a
single reduced surface field (RESURF) laterally-diffused metal
oxide semiconductor (LDMOS) configuration. FIGS. 9-13 respectively
illustrate alternative embodiments of the high-voltage
semiconductor device having other HVJT configurations. For the sake
of consistency and clarity, similar components appearing in FIGS.
2-8 are labeled the same throughout FIGS. 9-13.
[0040] FIG. 9 illustrates a diagrammatic fragmentary
cross-sectional side view of an embodiment of a high-voltage
semiconductor device having a double RESURF LDMOS HVJT
configuration. Here, the HVJT devices 130A-131A include doped wells
220-221, respectively. The doped wells 220-221 each have a doping
polarity that is opposite from the doping polarity of the N-drift
region 50. Thus, in the illustrated embodiment, the doped wells
220-221 are P-type wells. The doped wells 220-221 are formed
immediately below the isolation structures 80-81, respectively, and
at the top surface of the doped well 50. Hence, the doped wells
220-221 may also be referred to as P-top wells. The bottom surfaces
of the doped wells 220-221 form P/N junctions with the doped well
50. The P/N junctions can also help reduce the intensity of the
electric field in the high-voltage semiconductor device.
[0041] FIG. 10 illustrates a diagrammatic fragmentary
cross-sectional side view of an embodiment of a high-voltage
semiconductor device having a triple RESURF LDMOS HVJT
configuration. Here, the HVJT devices 130B-131B include doped wells
230-231, respectively. The doped wells 230-231 each have a doping
polarity that is opposite from the doping polarity of the N-drift
region 50. Thus, in the illustrated embodiment, the doped wells
230-231 are P-type wells. The doped wells 230-231 are formed below
the isolation structures 80-81, respectively, and are surrounded by
the doped well 50. Hence, the doped wells 230-231 may also be
referred to as buried P-wells. The top and bottom surfaces of the
doped wells 230-231 form P/N junctions with the doped well 50.
These P/N junctions can also help reduce the intensity of the
electric field in the high-voltage semiconductor device.
[0042] FIG. 11 illustrates a diagrammatic fragmentary
cross-sectional side view of an embodiment of a high-voltage
semiconductor device having a RESURF diode HVJT configuration. As
shown in FIG. 11, the RESURF diode HVJT devices 130C-131C are diode
structures, and therefore do not have gate structures. Anode and
cathode terminals may be formed on the heavily doped regions
112/113 and 110/111, respectively. FIG. 12 illustrates a
diagrammatic fragmentary cross-sectional side view of an embodiment
of a high-voltage semiconductor device having a different RESURF
diode HVJT configuration. As shown in FIG. 12, the RESURF diode
HVJT devices 130D-131D also contain doped wells 220-211 (P-top
wells), respectively. FIG. 13 illustrates a diagrammatic
fragmentary cross-sectional side view of yet another embodiment of
a high-voltage semiconductor device having another RESURF diode
HVJT configuration. As shown in FIG. 13, the RESURF diode HVJT
devices 130E-131E also contain doped wells 230-231 (buried
P-wells), respectively. These various embodiments of the
high-voltage semiconductor device offer similar breakdown
improvements as the embodiment discussed above with reference to
FIGS. 2-8.
[0043] It is understood that additional embodiments may exist, but
they are not discussed in detail herein. For example, the field
plates of the HVJT devices may have various shapes, sizes, and
locations. The various doped wells and regions may also have
different dimensions and doping concentration levels. It is also
understood that additional fabrication processes may be performed
to complete the fabrication of the semiconductor device shown in
FIGS. 2-13. For example, the semiconductor device may undergo
passivation, wafer acceptance testing, and wafer dicing processes.
For the sake of simplicity, these additional processes are not
shown or discussed herein either.
[0044] Referring now to FIG. 14, a simplified top view of an
embodiment of a resistor device 250A is illustrated. The resistor
device 250A is formed according to various aspects of the present
disclosure discussed above. In this embodiment, the resistor device
250A has an elongated zig-zag shape, or an S-shape. The resistor
device 250A has two opposite distal ends 260 and 270. The distal
ends 260 and 270 are electrically coupled to terminals 280 and 290,
respectively. A high voltage may be applied to the terminal 280
while the terminal 290 is grounded, or vice versa. Thus, a high
voltage potential exists across the resistor device 250A through
the terminals 280 and 290. The resistor device 250A has a midpoint
300 that is equidistant (in terms of distance along the resistor
250A, rather than absolute distance between two points) from the
two distal ends 260 and 270. According to the various aspects of
the present disclosure, a high voltage N-well underneath the
resistor device 250A may be electrically coupled to the midpoint
300, or close to it (for example within 10% of the total length of
the resistor device 250A). As discussed above, such configuration
allows the resistor device 250A to have better breakdown
performance--it can tolerate a higher voltage before breakdown
occurs.
[0045] FIG. 15 illustrates another simplified top view of an
embodiment of a resistor device 250B. The resistor device 250B is
formed according to various aspects of the present disclosure
discussed above. In this embodiment, the resistor device 250B has
an elongated square shape. The resistor device 250B has two
opposite distal ends 330 and 340. The distal ends 330 and 340 are
electrically coupled to terminals 350 and 360, respectively. A high
voltage may be applied to the terminal 350 while the terminal 360
is grounded, or vice versa. Thus, a high voltage potential exists
across the resistor device 250B through the terminals 350 and 360.
The resistor device 250B has a midpoint 370 that is equidistant (in
terms of distance along the resistor 250B, rather than absolute
distance between two points) from the two distal ends 330 and 340.
According to the various aspects of the present disclosure, a high
voltage N-well underneath the resistor device 250B may be
electrically coupled to the midpoint 370, or close to it (for
example within 10% of the total length of the resistor device
250B). For reasons similar to those discussed above with reference
to FIG. 6, such configuration allows the resistor device 250B to
have better breakdown performance.
[0046] FIG. 16 illustrates another simplified top view of an
embodiment of a resistor device 250C. The resistor device 250C is
formed according to various aspects of the present disclosure
discussed above. In this embodiment, the resistor device 250C has
an elongated spiral shape. The resistor device 250C has two
opposite distal ends 410 and 420. The distal ends 410 and 420 are
electrically coupled to terminals 430 and 440, respectively. A high
voltage may be applied to the terminal 430 while the terminal 440
is grounded, or vice versa. Thus, a high voltage potential exists
across the resistor device 250C through the terminals 430 and 440.
The resistor device 250C has a midpoint 450 that is equidistant (in
terms of distance along the resistor 250C, rather than absolute
distance between two points) from the two distal ends 410 and 420.
According to the various aspects of the present disclosure, a high
voltage N-well underneath the resistor device 250C may be
electrically coupled to the midpoint 450, or close to it (for
example within 10% of the total length of the resistor device
250C). For reasons similar to those discussed above with reference
to FIG. 6, such configuration allows the resistor device 250C to
have better breakdown performance.
[0047] FIG. 17 illustrates another simplified top view of an
embodiment of a resistor device 250D. The resistor device 250D is
formed according to various aspects of the present disclosure
discussed above. In this embodiment, the resistor device 250D has
an elongated zig-zag shape, or an S-shape. The resistor device 250D
has two opposite distal ends 460 and 465. The distal ends 460 and
465 are electrically coupled to terminals 470 and 475,
respectively. A high voltage may be applied to the terminal 470
while the terminal 475 is grounded, or vice versa. Thus, a high
voltage potential exists across the resistor device 250D through
the terminals 470 and 475. The resistor device 250D has a midpoint
480 that is equidistant (in terms of distance along the resistor
250D, rather than absolute distance between two points) from the
two distal ends 460 and 465. According to the various aspects of
the present disclosure, a high voltage N-well underneath the
resistor device 250D may be electrically coupled to the midpoint
480, or close to it (for example within 10% of the total length of
the resistor device 250D). As discussed above, such configuration
allows the resistor device 250D to have better breakdown
performance--it can tolerate a higher voltage before breakdown
occurs.
[0048] The resistor device 250D has a high-voltage junction ring
485. The high voltage junction ring 485 surrounds the elongated
resistor device in the top view. In an embodiment, the high voltage
junction ring 485 includes the HVJT device as discussed above. The
high voltage junction ring 485 has a ring width 170 that is in a
range from about 5 um to about 100 um.
[0049] FIG. 18 is a chart 500 illustrating the relationship between
breakdown voltage and the biased voltage of the high voltage
N-well. An X-axis of the chart 500 represents the amount of bias
voltage at the high voltage N-well below the resistor device. This
bias voltage varies depending on where in the resistor device the
high voltage N-well is tied to. A Y-axis of the chart 500
represents the breakdown voltage (BV). For example, at point 510,
the high voltage N-well is tied to a point on the resistor device
that is 0.1*L away from the high voltage distal end, where L=total
length of the resistor device. Thus, the bias voltage of the N-well
at point 510 is 0.9*VH, where VH=voltage difference applied across
the resistor device. Since point 510 is relatively close to the
distal end and not close to the midpoint of the resistor device,
the breakdown voltage at point 510 is not optimal--slightly less
than about 400 volts in this case.
[0050] Similarly, at point 520, the high voltage N-well is tied to
a point on the resistor device that is 0.3*L away from the high
voltage distal end, and the bias voltage of the N-well at point 520
is 0.7*VH. Since point 520 is closer to the midpoint of the
resistor device than point 510, the breakdown voltage at point 520
is better--slightly greater than about 520 volts in this case--even
though it is still not optimal yet.
[0051] At point 530, the high voltage N-well is tied to
approximately the midpoint of the resistor device, and the bias
voltage of the N-well at point 530 is 0.5*VH. The breakdown voltage
at point 530 is now substantially optimal and reaches about 730
volts.
[0052] At points 540 and 550, the high voltage N-well is tied to
points on the resistor device that is 0.7*L away and 0.9*L away
from the high voltage distal end (or 0.3*L away and 0.1*L away from
the low voltage distal end), respectively. Thus, the bias voltage
at points 540 and 550 are at 0.3*VH and 0.1*VH, respectively, and
the breakdown performance of the resistor device at points 540 and
550 once again begin suffer. Thus, from the chart 500, it can be
seen that the resistor device tends to reach optimal breakdown
performance when the high voltage N-well is tied close to the
midpoint of the resistor device.
[0053] FIG. 19 is a chart 600 illustrating the breakdown voltage.
An X-axis of the chart 600 represents the source-to-drain voltage
(Vds), which is also the voltage across the high-voltage resistor
device discussed herein. The Y-axis of the chart 600 represents the
source-to-drain current (Ids), which is also the current in the
high-voltage resistor device discussed herein. If the resistor
device is functioning properly, Vds and Ids should have a linear
relationship, as Vds=Ids*R, where R is the resistance of the
resistor device. However, if the resistor device has suffered a
breakdown, then the relationship between Vds and Ids is no longer
linear.
[0054] The chart 600 contains a plot curve 610, which represents a
simulation result of a Vds-Ids curve corresponding to an embodiment
of the high-voltage semiconductor device. As is illustrated, the
resistor device associated with plot curve 610 experiences device
breakdown--where Ids begins to "shoot" upward--when Vds is about
1000 volts. This breakdown voltage is a significant improvement
over the breakdown voltage offered by conventional high-voltage
resistor devices.
[0055] It is understood that various factors may influence the
breakdown voltage. For example, changing the size (or lateral
dimension) of the N-drift region may affect the breakdown voltage.
Changing the HVJT device may also affect the breakdown voltage. An
optimum configuration may be chosen according to design and
manufacturing concerns.
[0056] The embodiments discussed above offer advantages over
conventional high voltage devices, it being understood that
different embodiments may offer different advantages, and that no
particular advantage is required for all embodiments. One advantage
is that through proper biasing of the high voltage N-well, the
breakdown performance of the resistor device can be significantly
improved.
[0057] Another advantage is that, by incorporating HVJT devices,
electric field intensity is reduced, which can increase the
breakdown voltage to over 1000 volts. Furthermore, the N-well
biasing discussed above can also in effect double the breakdown
voltage (if the midpoint of the resistor is electrically coupled to
the N-well). As such, the breakdown voltage can be increased to
2000 volts.
[0058] Yet another advantage is that the biasing of the high
voltage N-well and the formation of the HVJT devices require no
additional fabrication processes and are compatible with existing
process flow. Thus, the implementation of the embodiments discussed
herein does not increase costs.
[0059] One of the broader forms of the present disclosure involves
a semiconductor device that includes: a substrate containing a
first doped region and a second doped region, the first and second
regions being oppositely doped; a first isolation structure and a
second isolation structure each disposed over the substrate, the
first and second isolation structures being spaced apart from one
another; a resistor disposed over at least a portion of the first
isolation structure; and a field plate disposed over at least a
portion of one of the first and second doped regions.
[0060] Another one of the broader forms of the present disclosure
involves a semiconductor device that includes: a substrate that
includes a doped well disposed therein, the doped well and the
substrate having opposite doping polarities; an insulating device
disposed over the doped well; an elongate resistor disposed over
the insulating device, a non-distal portion of the resistor being
coupled to the doped well; and a high-voltage junction termination
(HVJT) device disposed adjacent to the resistor.
[0061] One more of the broader forms of the present disclosure
involves a method of fabricating a high voltage semiconductor
device. The method includes: forming a first doped region in a
substrate; forming a second doped region in the substrate, the
second doped region being oppositely doped from the first doped
region, wherein an interface between the first and second doped
regions forms a P/N junction; forming first and second isolation
structures over the first doped region; forming a resistor device
over the first isolation structure; and forming a field plate at
least partially over the second isolation structure, the field
plate being disposed over the P/N junction.
[0062] In some embodiments, an exemplary semiconductor device
includes a first doped region and a second doped region disposed in
a substrate. The first doped region and the second doped region are
oppositely doped and adjacently disposed in the substrate. A first
isolation structure and a second isolation structure are disposed
over the substrate, such that each are disposed at least partially
over the first doped region. The first isolation structure is
spaced apart from the second isolation structure. A resistor is
disposed over a portion of the first isolation structure and
electrically coupled to the first doped region. A field plate
disposed over a portion of the second doped region and electrically
coupled to the second doped region.
[0063] In some embodiments, an exemplary semiconductor device
includes a diode-based high-voltage junction termination (HVJT)
device and a resistor electrically coupled to the diode-based HVJT
device. The diode-based HVJT device includes a first doped region
and a second doped region disposed in a substrate, the first doped
region and the second doped region having opposite doping
polarities and being adjacently disposed in the substrate, a
cathode terminal electrically coupled to the first doped region,
and an anode terminal electrically coupled to the second doped
region. The semiconductor device can further include an isolation
structure disposed over a portion of the first doped region, and
the resistor may be disposed over a portion of the isolation
structure.
[0064] The foregoing has outlined features of several embodiments
so that those skilled in the art may better understand the detailed
description that follows. Those skilled in the art should
appreciate that they may readily use the present disclosure as a
basis for designing or modifying other processes and structures for
carrying out the same purposes and/or achieving the same advantages
of the embodiments introduced herein. Those skilled in the art
should also realize that such equivalent constructions do not
depart from the spirit and scope of the present disclosure, and
that they may make various changes, substitutions and alterations
herein without departing from the spirit and scope of the present
disclosure.
* * * * *